This invention relates generally to metallurgical furnaces and more specifically to what is herein termed a lancing apparatus for blowing air or oxygen into a top-blown metallurgical furnace, such as in the basic oxygen steelmaking process, through a lance or pipe inserted therein through its mouth. Even more specifically, the invention is directed to means for facilitating the replacement or renewal of the lance as the same is consumed by fusion and/or corrosion within the furnace.
As is well known, the desired metallurgical reactions within the furnace under consideration are carried out at such high temperatures that a lance inserted therein inevitably suffers gradual fusion from its tip, even if the lance is made of metal having a high melting point and further specially treated for affording corrosion resistance at high temperatures. As the lance is consumed, that is, shortens to a certain specifiable point, by the progress of the gradual fusion, the same is detached from the lancing apparatus holding its top end, either in situ or after having been withdrawn out of the furnace. A new lance is then inserted into the apparatus, and the top end of the consumed lance is screw-threadedly or otherwise jointed to the bottom end of the new lance. The thus-renewed lance is again inserted into the furnace for recommencement of the oxygen lancing operation.
Thus, where a number of lances are required, as for use in large smelting furnaces operating at extremely high temperatures, the renewal of the consumed lances can be effected only at the expense of substantial time and labor. What is worse, prolonged downtime must be imposed upon the furnaces, resulting in a significant decrease in their production rates.